Fault diagnosis system for electronic device on automobiles

ABSTRACT

A fault diagnosis system is provided for vehicles having a pluarlity of automotive electronic devices which output fault diagnoses according to one of a plurality of output signal schemes disposed thereon. A vehicle-side connector includes pins for carrying signal lines for signals representing the results of the fault diagnoses output from the plurality of of electronic devices. The vehicle-side connector also includes at least one pin for carrying at least one control line for a signal designating a selected output signaling scheme to the electronic devices. One of a plurality of testers displays the results of the fault diagnoses on the basis of the signals transmitted from the respective electronic devices. Each tester has a tester-side connector which connects to the vehicle-side connector to connect the output signals from each of the electronic devices and the control signal for designating the selective signaling scheme.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fault diagnosis system which permitseasy fault diagnosis of various automotive electronic devices.

Hitherto, fault diagnoses of electronic devices on automobiles have beenconducted by connecting those devices to a tester via a pair ofcorresponding connectors which include a vehicle-side connector and atester-side connector. The vehicle-side connector has a predeterminednumber of pins corresponding to the number of electronic devices and isconnected to the electronic devices by a corresponding set of signallines for transmitting therebetween signals representing the results offault diagnosis of corresponding electronic devices and controllingsignals from the tester. The tester-side connector also has acorresponding number of pins and is connected to the tester by anotherset of signal lines for transmitting therebetween the control signalsfrom the tester and signals from the vehicle-side connector for display.

Consequently, if the number of electronic devices mounted in theautomobile increases, the number of pins of both connectors mustcorrespondingly be increased to accomodate the additional signal lines.

In addition, when the system of an electronic device has undergone achange, signals from the connector also undergo change, so that itsometimes becomes necessary to change the number of pins of theconnectors and as well as alter the connections of the tester-sideconnector pins on each such occasion.

As a result, from a long-term perspective, compatible testers whichideally could be used for a wide variety of eleectronic fault diagnosissystems have not been available. Hence, it has been necessary to developa special tester each time the fault diagnosis system changes.Accordingly there have been many wasteful factors such as differenttesters being prepared for different vehicle types and yearly modelchanges.

Next, a description will be made of a conventional fault diagnosistester. FIG. 1 is a block diagram illustrating the configuration of aconventional fault diagnosis system. In FIG. 1, respective signal lines9, 10, 11 and 12 are connected to a vehicle-side connector 5 fromelectronic devices 1, 2, 3, 4 which are control units for controllingvarious types of systems mounted on an automobile. In order to connectON-OFF signals from the electronic devices 1, 2, 3 and 4 to a tester 7,a tester-side connector 6 which is connected to the tester 7 throughsignal lines 14, 15, 16 and 17 is connected to the vehicle-sideconnector 5. If a fault has occurred in any of the electronic devices 1to 4, the result is diagnosed by the tester 7, and a code is displayedon a diplay 8 on the tester 7.

With the conventional fault diagnosis system, the electronic devices 1-4are connected to each other as shown in FIG. 1. Thus, in cases where thenumber of systems is increased or a signaling system undergoes a change,it is necessary to change the number of pins at the vehicle-sideconnector 5 and the tester-side connector 6 for each such occasion. Inaddition, it is necessary to change the signal processing method of thetester 7 with respect to each terminal. Therefore, there have beendrawbacks in that the testers become more specialized, pins must berearranged or newly added, and that installation costs tend to becomehigher.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide a faultdiagnosis system for automotive electronic devices which accommodateschanges in the signaling system, allows the components of the system tobe consolidated or added to, allows conventional-type testers to be usedwithout modification, and also allows new types of testers to use thesame connector, thereby overcoming the above-described drawbacks of theprior art.

In keeping with this aspect of the present invention, there is provideda fault diagnosis system for comprising a plurality of electronicdevices mounted on the automobiles having corresponding signal lines andoutputting the results of their fault diagnosis according to an outputsignaling schemes, at least one control line connected to the electronicdevices and transmitting a signal selecting the output signal scheme, avehicle-side connector connected to the signal lines and the controlline, and a plurality of testers adapted to designate the outputsignaling scheme and to display results of fault diagnosis transmittedfrom the respective electronic devices in accordance with the designatedoutput signaling scheme, each of the testers having a tester-sideconnector to be selectively connected to the vehicle-side connector forlinking the signal lines and the control line between the electronicdevices and the testers. In a preferred embodiment of the invention,signals representing the results of the fault diagnosis output fromelectronic devices on automobiles are converted from ON-OFF signals intoserial signals by short-circuiting the control signal line to agrounding line inside the tester.

The above and other objects, features and advantages of the presentinvention will become clear from the following description of thepreferred embodiment when the same is read in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a conventional fault diagnostic tester;

FIG. 2 is a block diagram illustrating the configuration of anembodiment of a fault diagnosis system for automotive electronic devicesin accordance with the present invention; and

FIG. 3 is a schematic view showing another embodiment of the connector.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the accompanying drawings, description will be made ofan embodiment of a fault diagnosis system for automotive electronicdevices according to the present invention. FIG. 2 is a block diagramillustrating the configuration thereof. In this drawing, electronicdevices 1-4, such as control units, are mounted on a vehicle arerespectively connected through the signal lines 9-12 to a vehicle-sidefault diagnosis connector 25, in which signals representing the resultsof fault diagnosis are collected from the electronic devices 1-4. Theelectronic devices 1-4 to be diagnosed themselves may be of aconventional design and are capable of outputting either ON-OFF signalsor serial signals which have a higher speed than the ON-OFF signals.Many conventional automotive electronic devices generally have hadfunction for outputting not only ON-OFF signals but also serial signals.Each of the electronic devices 1-4 is connected to the vehicle-sidediagnosis connector 25 through a common control line 20 and through therespective signal lines 9-12. The control line 20 is connected to aconnecting pin 21 mounted in the connector 25.

According to the illustrated embodiment of the fault diagnosis system ofthe present invention, either one of two kinds of testers 7 and 29 canbe utilized. The tester 7 which is identical to that shown in FIG. 1judges and displays the results of fault diagnosis by means of theON-OFF signals just in the same manner as in the system shown in FIG. 1.The tester 29 displays the results of fault diagnosis by means of serialsignals having a higher speed that that of ON-OFF signals. The tester 29therefore is provided with a connector 28 having a connecting pin 33 towhich a grounded line 32 is connected. The other end of the groundedline 32 is grounded within the tester 29. The tester 29 is provided witha display 30 for displaying the results of the diagnosis through the useof the serial signals. The tester 29 is also provided with signal lines14-17 for connection to the connector 28 which is connectable to thevehicle-side connector 25.

When the tester 7 is connected to the electronic devices 1-4 through theconnector 6 and the connector 25, all the signal lines 9-12 and 14-17are connected respectively, but the control line 20 remains unconnectedand the voltage of the control line 20 floats to a floating voltage.Therefore, the electronic devices 1-4 provide normal ON-OFF signals tothe tester 7 through the signal lines 9-12, the connectors 25 and 28,and the signal lines 14-17.

When the tester 29 is connected to the electronic devices 1-4 throughthe connectors 28 and 25, the grounded line 32 and the control line 20are connected together in addition to the signal lines 9-12 and 14-17.Therefore, control line 20 becomes grounded and each of the electronicdevices 1-4 detect this. In response, each of the electronic devices 1-4changes its signal supplying mode to provide serial signals rather thanON-OFF signals.

Next, description will be made of operation in accordance with thepresent invention. The results of fault diagnosis are normally outputfrom the electronic devices 1-4 to the vehicle-side fault diagnosisconnector 25. Consequently, the conventional-type tester 7 receivesthese results of fault diagnosis via the connector 6 and displaysdiagnosed faults on the display 31.

The control line 20 which directs the electronic devices to provideeither ON-OFF signals or serial signals may be connected to the piston13 of the terminal of the connector 6 as shown in FIG. 3. The pin at theposition 13 is made a spare pin, and does not lead to the tester 7, sothat signals from the electronic devices 1-4 permit fault diagnosisusing a conventional-type tester. In addition, there is an advantage inthat, if the pin at the position 13 is made a spare pin or is set in anon-connected state, fault diagnosis can be carried out by measuringeach terminal of the vehicle-side fault diagnosis connector 25 using anordinary voltmeter even if the tester 7 is not connected.

Description will now be given of cases where fault diagnosis is effectedusing serial signals, i.e., where the tester 29 for effecting diagnosisby means of serial signals is connected to the vehicle-side faultdiagnosis connector 25. The control line 20 for changing over ON-OFFsignals to serial signals is connected to the serial signal-use tester29 via a line 32 running from the connector 28 to the tester 29 as seenin FIG. 2. When the vehicle-side fault diagnosis connector 25 and theconnector 28 are connected, the line 32 is short-circuited to agrounding line inside the tester 29 so as to change the voltage level ofthe control line 20. Hence, the signal generating mode of the electronicdevices 1-4 are shifted from the ON-OFF signal mode into the serialsignal mode.

In other words, by changing the voltage level of one pin of theconnector, i.e., the voltage level of the pin to which the control line20 is connected, distinction between the conventional-type tester 7 andthe serial signal-use tester 29 can be determined by the respectiveelectronic devices. In response, the devices 1-4 change over the type ofsignal used for fault diagnosis.

When the conventional-type tester 7 is used, if the pin connected to thecontrol line 20 remains unconnected, i.e. does not have a correspondingpin in the connector 6 so that there is no connection thereof to thetester 7, it is possible to read ON-OFF signals even when the connector6 is fitted with the tester 7, thereby allowing the function of theconventional-type tester 7 to be domonstrated.

In the above, description has been made of an automobile fault diagnosissystem which is capable of effecting transmission of two or more modesby changing the system of signals issued from electronic devices bycausing changes in the voltage level of a specific terminal. As for thecontents of signals, description has been made of transmitting ON-OFFand serial signals, but, by increasing the number of specific pins totwo or more, it is possible to switch over a multiplicity of signalingsystems more numerous than in the above-described case, therebyeffecting a wider range of changeover.

As has been described, the fault diagnosis system in accordance with thepresent invention for automotive electronic devices, in which a commonconnector is installed at similar places or positions for each vehicleand signals from this connector are used, makes it possible to receivean ON-OFF signal in a state in which a connector of a diagnosis testeris not inserted into a vehicle-side fault diagnosis connector as well asmaking it possible to receive the contents of the totally differentserial signal appearing at the vehicle-side fault diagnosis connectorwhen the connector of the diagnosis tester is inserted even when thepins are the same. Therefore, even when the electronic devices areidentical, two or more kinds of testers can be used, so that developmentof specialized use testers is no longer required. In addition,conventional testers can also be used via the same connector, and thecosts required for testers in general can be reduced.

What is claimed is:
 1. A fault diagnosis system for an automobile comprising:at least one automotive electronic device mounted on an automobile which performs a fault diagnosis on the automobile, the electronic device having a signal line for outputting signals representing results of the fault diagnosis according to either one of a plurality of output signaling schemes and having a control line for inputting a signal selecting the output signal scheme; a vehicle-side connector connected to the signal line and the control line; a first tester adapted to a first one of the plurality of output signaling schemes and having a display for displaying results of the fault diagnosis transmitted from said electronic device in accordance with the first output signaling scheme, the first tester having a first tester-side connector which can be connected to said vehicle-side connector for linking the signal .[.lines.]. .Iadd.line .Iaddend.and the control line between said electronic device and said first tester, the first tester providing a first signal for designating the first output signaling scheme to said control line; and a second tester adapted to a second one of the plurality of output signaling schemes and having a display for displaying results of the fault diagnosis transmitted from said electronic device in accordance with the second output signaling scheme, the second tester having a second tester-side connector which can be connected to said vehicle-side connector for linking the signal .[.lines.]. .Iadd.line .Iaddend.and the control line between said electronic device and said second tester, the second tester providing a second signal for designating the second output signaling scheme to said control line; wherein either one of said tester-side connectors of said testers can be selectively connected to said vehicle-side connector.
 2. A fault diagnosis system according to claim 1 wherein:the first tester is wired to provide a floating voltage over the control line, and the second tester is wired to connect the control line to a grounding point. 